A non-IBM mainframe that runs IBM mainframe operating systems and applications. In the late 1960s, RCA's computer division produced the Spectra 70, the first line of machines compatible with IBM's System/360. Later, Amdahl, National Semiconductor (marketed through Itel) and Hitachi entered this segment. Today, IBM-compatible mainframes are no longer manufactured. Although servers from HP, Sun and others offer mainframe-like features, IBM is the only company making IBM mainframes. See HDS and Amdahl.